Watcher for absence of data in given time

I have been trying to write a watcher for when my logstash instances go down. Obviously I cant write one to query a field, but need to write it for the lack of data for a given index for a period of time. I have tried several iterations, but none of these work.

    "query": {
        "bool": {
          "must": [
            {
              "query_string": {
                "default_field": "host",
                "query": "*MON011080*"
              }
            },
            {
              "query_string": {
                "default_field": "host",
                "query": "*MON011080*"
              }
            }
          ],
          "filter": {
            "range": {
              "@timestamp": {
                "from": "now-8m",
                "to": "now"
              }
            }
          }
        }
      }

Also tried it with exists, but that doesnt seem to work either. Can anyone steer me in the right direction?